Conventionally, multiple electronic control units (ECUs) are mounted to a vehicle and are connected with each other via a network such as a controller area network (CAN).
The multiple ECUs perform individual processing while exchanging information through the network. In recent years, the scale of in-vehicle networks tends to be increased, where such a structure is often employed that multiple small-sized networks are connected to a relay device such as a gateway, which relays a message between the networks.
Japanese Patent Application Laid-Open No. 2014-86812 describes a CAN system which aims to enhance fault tolerance by transmitting a retransmission request frame if the first node in the CAN system fails to receive a frame and is in an error passive state, storing the frame transmitted to a communication line in the second node, and retransmitting the frame for which retransmission is requested to the first node.
Japanese Patent Application Laid-Open No. 2011-103577 describes a communication system that aims to prevent erroneous operation on the reception side of a frame with a configuration where a CAN controller measures a transmission latency from the input of a frame to the start of transmission to a communication line and transmits the frame together with information related to the transmission latency, while the CAN controller that received the frame decides processing to be executed in accordance with the transmission latency.